分布式存储中一种新的低修复带宽的Hitchhiker码

为了高效可靠的存储海量数据,分布式存储系统常利用纠删码来降低存储开销.Hitchhiker码是Piggybacking架构下易于工程实现的双条带MDS(Maximum Distance Separable Code)码,具有参数(k,r)取值任意、修复成本较低等特征.然而,目前Hitchhiker码只优化了数据单元的修复带宽,未优化校验单元的修复带宽.针对此问题,本文提出了利用LRC(Locally Repairable Code)的思想同时优化数据单元和校验单元的编码(Hitchhiker-LRC和Hitchhiker-LRC+).该方法是对第一个子条带中l个校验求局部校验,将其存放在第一个子条带的某个校验上,要求该校验的数据已通过局部校验的形式捎带在了第二个子条带的后r-1个校验中,并且对该校验单元做了横向减法.最后,理论和实验证明,Hitchhiker-LRC和Hitchhiker-LRC+这两种编码在2≤r<k/2时可降低1%~5%修复带宽和节省约10%的修复时间,在k/2≤r<k时,Hitchhiker-LRC+在r较大时,相比Hitchhiker-LRC具有更低的修复带宽;并存在l使得修复带宽率达到最优.

异构对等分布式存储中的DHitchhiker码

具有高可用性和安全性的去中心化存储因其应用的相同参数低码率RS(Reed-Solomon codes)码存在修复带宽较高的问题.对此,提出一种基于可信度的低修复带宽DHitchhiker码.首先将Hitchhiker码的第一子条带中的数据节点和部分校验节点捎带在余下的校验节点的第二个子条带上;接着将节点分类,让高可信节点存储余下的校验节点,低可信节点存储数据节点和部分校验节点,并让不同类型的节点采用不同的修复策略;最后理论结合实验证明,在修复低可信节点时,DHitchhiker可降低约25%的修复带宽;在整体上,未分类存放的DHitchhiker码可降低约0.5%的修复带宽,基于可信度的DHitchhiker码可降低约1%的修复带宽和2.5%~3.3%的修复时间.

基于分布式存储的OHitchhiker码

为推进纠删码在分布式存储系统中的应用,研究提高系统修复效率的算法。Hitchhiker码作为一种最新的具有最优存储空间和较低修复成本的纠删码,已在Hadoop等分布式系统中部署实现。针对目前Hitchhiker码采用均分的数据分配模式,存在网络带宽浪费的问题,提出一种最优分配的Hitchhiker编码(optimal allocation of Hitchhiker,OHitchhiker)。通过在编码的分配环节引入一种动态选择分配算法,使得OHitchhiker码可以针对不同(n,k)值选择具有最小修复代价的编码结构。理论分析以及实验结果验证了OHitchhiker码在保持较低存储空间的同时,进一步降低了下载带宽。

Cretaceous Hitchhikers:a Possible Phoretic Association between a Pseudoscorpion and Bird in Burmese Amber

Objective Phoresy represents a non-parasitic association between animals of different taxa related to transportation. Members of several pseudoscorpion families are phoretic. In pseudoscorpions, phoresy may or may not be associated with their predatory behavior, enabling dispersal over larger distances than they could manage with their own short legs. This provides a wide distribution, and a potential food supply.

高级脉冲等离子推力器在强力Ⅱ.1上的验证

本文描述在有关各方的共同努力下,高级PPT(脉冲等离子推力器)在将于1999年1月发射的强力Ⅱ.1(MightySatⅡ.1)空间飞行中的验证工作的进展,当前正在为这次飞行研制的PPT与以前的经飞行验证的模型相比,在技术上代表了一次大踏步的前进。虽然强力Ⅱ.1卫星的运载工具还没有最后确定,目前暂时考虑采用航天飞机Hitchhiker弹射系统(HES)。在选择这种发射系统的情况下,通过用PPT提升强力Ⅱ.1卫星的轨道,将使它在1年内显著提高在轨寿命1～3个月。由于PPT的高比冲(>1000s)、低系统质量(<5kg),而且当无动力时具有惰性性质(这是减少航天飞机组装要求的关键),PPT是增加小卫星寿命理想的推进系统。除了增加任务的寿命,还专门设计了在轨操作规程以严格试验PPT并验证它与强力Ⅱ.1卫星的相容性,为未来在国防部、NASA和商用卫星上的应用进行确认。

Hitchhiking Effect Mapping: A New Approach for Discovering Agronomic Important Genes

Besides the natural selection, the crops cultivated today have experienced two episodes of strong artificial selection, domestic and modern breeding. Domestication led to giant genetic structure differentiation between cultivars and their wild species, while modern breeding made further genetic structure differentiation between the modern varieties and the landraces. In a population, diversity of the loci under strong selection is significantly lower than that of other loci. At the same time, diversity in the genomic regions flanking these selected loci also declines in the process of selection. This phenomenon is called hitchhiking effects or selection sweep in genetics. Genomic regions with selection sweep （haplotype block） could be detected after draft genome scanning （genome typing） with molecular markers in a number of released varieties or natural populations. Marker/trait association analysis in these regions would detect the loci （or QTLs） even the favored alleles （genes） in breeding or natural adaptation. Fine scanning of these genomic regions would help to determine the sizes of haplotype blocks and to discover the key genes, thereby providing very valuable information for isolation of the key genes and molecular design of new varieties. Establishment of high density genetic linkage maps in the major crops and availability of high throughput genotyping platform make it possible to discover agronomic important genes through marker/trait association analysis. On the basis of available publications, we give a brief introduction of the hitchhiking effect mapping approach in this paper using plant height, 1 000-grain weight, and phosphorus-deficiency tolerance as examples in wheat.

Self-oriented central-tumor delivery of legumain-cleavable vehicles governed by circulating monocyte/macrophage for precise tumor enrichment and immune activation

Compressed blood and intratumoral lymphatic vessels induced by proliferated tumor cells and elevated interstitial fluid pressure produce regional hypoxic and necrotic region within tumors,which severely reduced the accessibility of immunogenic cell death(ICD)related drugs and immune-related cells.Herein,the strategy of self-oriented deep tumor delivery by circulating monocyte/macrophage was proposed.Briefly,CS-AI including an indoleamine 2,3-dioxygenase(IDO)inhibitor indoximod(IND)and hydrophilic chitosan(CSO)linked with alanine-alanine-asparagine(AAN)was prepared,which could be selectively cleaved by legumain overexpressed in macrophages and promote the collapse in structure.Then,CS-AI was modified with mannose on the surface and further encapsulated the ICD inducer doxorubicin(DOX)to obtain M-CS-AI/DOX.Upon intravenous injection,MCS-AI/DOX was specially recognized and internalized by circulating monocyte in vivo.The formed drugs/monocyte tend to distribute in hypoxia/necrosis region guided by the homing signals released by tumor.Accumulated monocytes then further differentiated into macrophages,up-regulating the expression of legumain and promoting the sensitive-release of chemo-drug DOX,IND,and the mannose-modified CSO(M-CSO).The released IND would specifically regulate immunosuppressive tumor microenvironment,and synergistically inhibit tumor growth with immune activation elements,ICD-induced DOX,and the favorable adjuvant M-CSO.In summary,the self-oriented deep tumor delivery of legumain-cleavable nanovesicles through circulating monocyte makes it possible for reaching tumor regions inaccessible for nanoparticles and provides a novel insight for precise tumor enrichment and immune activation.

Salmonella-mediated blood-brain barrier penetration,tumor homing and tumor microenvironment regulation for enhanced chemo/bacterial glioma therapy

Chemotherapy is an important adjuvant treatment of glioma,while the efficacy is far from satisfactory,due not only to the biological barriers of blood-brain barrier(BBB)and blood-tumor barrier(BTB)but also to the intrinsic resistance of glioma cells via multiple survival mechanisms such as upregulation of P-glycoprotein(P-gp).To address these limitations,we report a bacteria-based drug delivery strategy for BBB/BTB transportation,glioma targeting,and chemo-sensitization.Bacteria selectively colonized into hypoxic tumor region and modulated tumor microenvironment,including macrophages repolarization and neutrophils infiltration.Specifically,tumor migration of neutrophils was employed as hitchhiking delivery of doxorubicin(DOX)-loaded bacterial outer membrane vesicles(OMVs/DOX).By virtue of the surface pathogen-associated molecular patterns derived from native bacteria,OMVs/DOX could be selectively recognized by neutrophils,thus facilitating glioma targeted delivery of drug with significantly enhanced tumor accumulation by 18-fold as compared to the classical passive targeting effect.Moreover,the P-gp expression on tumor cells was silenced by bacteria typeⅢsecretion effector to sensitize the efficacy of DOX,resulting in complete tumor eradication with 100%survival of all treated mice.In addition,the colonized bacteria were finally cleared by anti-bacterial activity of DOX to minimize the potential infection risk,and cardiotoxicity of DOX was also avoided,achieving excellent compatibility.This work provides an efficient trans-BBB/BTB drug delivery strategy via cell hitchhiking for enhanced glioma therapy.

Characterization of the interaction of nanobubble ultrasound contrast agents with human blood components

Nanoscale ultrasound contrast agents,or nanobubbles,are being explored in preclinical applications ranging from vascular and cardiac imaging to targeted drug delivery in cancer.These sub-micron particles are approximately 10x smaller than clinically available microbubbles.This allows them to effectively traverse compromised physiological barriers and circulate for extended periods of time.While various aspects of nanobubble behavior have been previously examined,their behavior in human whole blood has not yet been explored.Accordingly,herein we examined,for the first time,the short and long-term effects of blood components on nanobubble acoustic response.We observed differences in the kinetics of backscatter from nanobubble suspensions in whole blood compared to bubbles in phosphate buffered saline(PBS),plasma,or red blood cell solutions(RBCs).Specifically,after introducing nanobubbles to fresh human whole blood,signal enhancement,or the magnitude of nonlinear ultrasound signal,gradually increased by 22.8±13.1%throughout our experiment,with peak intensity reached within 145 s.In contrast,nanobubbles in PBS had a stable signal with negligible change in intensity(1.7±3.2%)over 8 min.Under the same conditions,microbubbles made with the same lipid formulation showed a56.8±6.1%decrease in enhancement in whole blood.Subsequent confocal,fluorescent,and scanning electron microscopy analysis revealed attachment of the nanobubbles to the surface of RBCs,suggesting that direct interactions,or hitchhiking,of nanobubbles on RBCs in the presence of plasma may be a possible mechanism for the observed effects.This phenomenon could be key to extending nanobubble circulation time and has broad implications in drug delivery,where RBC interaction with nanoparticles could be exploited to improve delivery efficiency.

Impacts of climate warming on hybrid zone movement： Geographically diffuse and biologically porous ＂species borders＂

The ecology and evolutionary biology of insect-plant associations has real- ized extensive attention, especially during the past 60 years. The classifications （categorical designations） of continuous variation in biodiversity, ranging from global patterns （e.g., lat- itudinal gradients in species richness/diversity and degree of herbivore feeding specialization） to localized insect-plant associations that span the biospectrum from polyphenisms, polymorphisms, biotypes, demes, host races, to cryptic species, remain academically contentious. Semantic and biosystematic （taxonomical） disagreements sometimes detract from more important ecological and evolutionary processes that drive diversification, the dynamics of gene flow and local extinctions. This review addresses several aspects of insect specialization, host-associated divergence and ecological （including ＂hybrid＂） speciation, with special reference to the climate warming impacts on species borders of hybridiz- ing swallowtail butterflies （Papilionidae）. Interspecific hybrid introgression may result in collapse of multi-species communities or increase species numbers via homoploid hybrid speciation. We may see diverging, merging, or emerging genotypes across hybrid zones, all part of the ongoing processes of evolution. Molecular analyses of genetic mosaics and genomic dynamics with ＂divergence hitchhiking＂, combined with ecological, ethological and physiological studies of＂species porosity＂, have already begun to unveil some answers for some important ecological/evolutionary questions. （i） How rapidly can host-associated divergence lead to new species （and why doesn＇t it always do so, e.g., resulting in ＂incom- plete＂ speciation）？ （ii） How might ＂speciation genes＂ function, and how/where would we find them？ （iii） Can oscillations from specialists to generalists and back to specialists help explain global diversity in herbivorous insects？ （iv） How could recombinant interspecific hybridization lead to divergence and speciation？ From ancient phytochemically defined angiosperm affiliations to recent and very local geographical mosaics, the Papilionidae （swallowtail butterflies） have provided a model for enhanced understanding of ecological patterns and evolutionary processes, including host-associated genetic divergence, ge- nomic mosaics, genetic hitchhiking and sex-linked speciation genes. Apparent homoploid hybrid speciation in Papilio appears to have been catalyzed by climate warming-induced interspecific introgression of some, but not all, species diagnostic traits, reflecting strong divergent selection （discordant）, especially on the Z （= X） chromosome. Reproductive isolation of these novel recombinant hybrid genotypes appears to be accomplished via a delayed post-diapause emergence or temporal isolation, and is perhaps aided by the thermal landscape. Changing thermal landscapes appear to have created （and may destroy） novel recombinant hybrid genotypes and hybrid species.

Citywide package deliveries via crowdshipping:minimizing the efforts from crowdsourcers

Most current crowdsourced logistics aim to minimize systems cost and maximize delivery capacity,but the efforts of crowdsourcers such as drivers are almost ignored.In the delivery process,drivers usually need to take long-distance detours in hitchhiking rides based package deliveries.In this paper,we propose an approach that integrates offline trajectory data mining and online route-and-schedule optimization in the hitchhiking ride scenario to find optimal delivery routes for packages and drivers.Specifically,we propose a two-phase framework for the delivery route planning and scheduling.In the first phase,the historical trajectory data are mined offline to build the package transport network.In the second phase,we model the delivery route planning and package-taxi matching as an integer linear programming problem and solve it with the Gurobi optimizer.After that,taxis are scheduled to deliver packages with optimal delivery paths via a newly designed scheduling strategy.We evaluate our approach with the realworld datasets;the results show that our proposed approach can complete citywide package deliveries with a high success rate and low extra efforts of taxi drivers.

Cell relay-delivery improves targeting and therapeutic efficacy in tumors

Cell-mediated drug delivery system(CDDS)has shown great potential for cancer therapy.However,a single cell-mediated drug delivery mechanism has not generally been successful,particularly for systemic administration.To augment the antitumor therapy efficacy,herein,we propose a strategy of cell relay-delivery for the use of artificially damaging/aging erythrocytes to hitchhike on circulating monocytes/macrophages for intratumoral accumulation of anticancer drugs.This biomimetic relay-delivery strategy was derived from the manner in which circulating monocytes/macrophages in body specifically engulf damaged/senescent erythrocytes and actively transmigrate into the tumor bulk.The strategy elegantly combines the natural functions of both cells,which therefore provides a new perspective to challenge current obstacles in drug delivery.According to the strategy,we developed biotinylated erythrocyte-poly(lactic-co-glycolic acid)(PLGA)nanoparticle hybrid DDSs(bE-NPs)using avidin-biotin coupling.In such a system,biotinylated erythrocytes can mimic the natural property of damaged/senescent erythrocytes,while PLGA NPs are capable of encapsulating anticancer drugs and promoting sustained drug release.Anticancer drugs can effectively target tumor sites by two steps.First,by using biotinylated erythrocytes as the carrier,the drug-loaded PLGA NPs could be specifically phagocytized by monocytes/macrophages.Second,by taking advantage of the tumor-tropic property of monocytes/macrophages,the drug-loaded PLGA NPs could be efficiently transported into the tumor bulk.After encapsulating vincristine(VIN)as the model drug,bE-NPs exhibited the most favorable antitumor effects in vitro and in vivo by the cell relay-delivery effect.These results demonstrate that the cell relay-delivery provides a potential method for improving tumor treatment efficacy.